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The Baryonic Effects on the Properties of Dark Matter Haloes

The Baryonic Effects on the Properties of Dark Matter Haloes. Weipeng Lin (Shanghai Astronomical Observatory,CAS) Collaborators: Shude Mao (Univ. of Manchester) Yipeng Jing(Shanghai Astro. Obs.) Liang Gao (NAOC).

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The Baryonic Effects on the Properties of Dark Matter Haloes

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  1. The Baryonic Effects on the Properties of Dark Matter Haloes Weipeng Lin (Shanghai Astronomical Observatory,CAS) Collaborators: Shude Mao (Univ. of Manchester) Yipeng Jing(Shanghai Astro. Obs.) Liang Gao (NAOC) The 9th Sino-German Workshop on Galaxy Formation and Cosmology, 26-29 April, 2011@HangZhou

  2. Basic Facts of Baryon • Universal baryon fraction of mass: ~16% (WMAP’s result) • DM dominates on large scale, while on small scale, there are spaces (e.g. halo center) where baryon are dominated, and important. • Baryon physics, 1st order: gas shock-heating, cooling, star formation, SN/AGN feedback, metal enrichment; 2nd order: heating by UV background & cosmic ray, evaporation, ram pressure stripping, gravitational heating, magnetic field, tidal stripping, heat conduction, turbulence, convection, etc. • Dynamics: AC effect, dynamical friction of sinking satellites, interaction between rotation disk/bars and halo matter, etc.

  3. What halo properties could be influenced by baryon physics? • Matter distribution (DM, stellar components, cold/hot gas) of halo, especially at central part of halo • Baryon/stellar fraction, temperature/entropy profiles • Shape of halo: density or potential well, x-ray halo • Properties of halo sub-structures • Angular momentum distribution and alignment (of gas, stars and DM) Extended: • Gravitational shear field • Alignment of matter distribution in DM halo，…… The effects are important for precise cosmology!

  4. What we have done so far? We have done a set of N-body/SPH simulations and studied following baryonic effects: • Clustering and weak lensing : Jing, et al. 2006, ApJ • Galaxy HOD: Zhu, et al. 2006 • Galaxy merging time-scale: Jiang et al. 2008 ApJ; A&A 2010 • Mass distribution and entropy profile: Lin et al. 2006, ApJ • Sunyave-Zel’dovich Effect (thermal and kinetic): Shao, et al. 2011a,b • Mass distribution, halo shape and alignment: Lin et al. , to be submitted

  5. Brief of simulations • LCDM (WMAP parameters), Box：100 Mpc/h • Gadget-v2 (Springel 2005) • A set of simulations using the same IC and all started from z=120, softening 4.5kpc (if not indicated) • Pure DM simulation 5123 (PDM, as reference) • Non-radiative (A4 or Gas512) 5123 DM + 5123 Gas • SF1: 5123 DM + 5123 Gas with cooling, SF, SNFB(9kpc/h) • SF2: 5123 DM + 5123 Gas with cooling, SF, SNFB(4.5kpc/h) • SF3: 5123 DM + 5123 Gas with cooling, SF, SNFB(4.5kpc/h), baryon fraction is reduced by half. The simulations were done at Shanghai supercomputer center.

  6. Lin, et al.,2006 ~10% ~3% Adiabatic A4(5123) Gadget-v2

  7. The case with Cooling,SF,SNFB Mass concentration increases by 10-20% Consistent with Duffy et al. 2010 in the case of no AGN feedback

  8. A: Pure Dark Matter B: Non-Radiative（A4） C: Star Formation（SF1） Evidence: 2-D halo shape C A B

  9. But, they used inertia tensor as shape indicator, easily affected by sub-structures Kazantzidis, et al., 2004, ApJ Letter, 611, L73-L76

  10. Baryonic Effect on Halo Potential Well (Abadi, et al., 2009, arxiv:0902.2477)

  11. The influence of baryon on tri-axial halo shape • DM halos are not spherical, nova method: tri-axial model for iso-density surface (Jing & Suto, 2002) • Baryon physics may change the shape of halos because of collision nature • In what degree can the baryon change halo shape?

  12. Results of axis ratio PDM: DM-only, NRG: Non-Radiative, SF: with gas cooling, star formation and SN feedback Force softening length: 4.5 kpc, except for SF1 (9.8 kpc) SF3: baryon fraction is reduced to 8%

  13. SFR NRG: Non-radiative gas SF1: softening length 9.8 kpc SF2: softening length 4.5 kpc SF3: softening length 4.5 kpc, but baryon fraction is 8%

  14. Shape changed Spherical Prolate Oblate Prolate  Spherical

  15. Two types of alignment • “central alignment”: The central alignment between the major axis of stellar components and that of total mass i.e. at radius of 15 kpc/h, or 5% Virial Radii • “overall alignment”: The alignment between the major axis of simulated brightest cluster galaxy (“BCG”) and that of the whole halo

  16. Projected stellar density contours Red circle with radius of 15 kpc/h Notice: The iso-photo twist

  17. 2D Density Map Total Mass Stellar Difference of Position Angle at r_e~15.0kpc: 0.22 Degree! Well-aligned

  18. Probability of Mis-alignment angle：central alignment (at 15 kpc/h) Observations: Sloan Lens ACS Survey (SLCAS) • Keeton et al., 98, <10 °(17 lensed galaxies) • Koopmans et al. 2006: 15 massive early-type galaxies, • <0°±3°>, rms of 10 °

  19. The alignment at 5% Virial Radii

  20. Baryon fraction LeftPanel: inside 15 kpc/h; Right Panel: inside 5% Rvir

  21. Rvir =1.78 Mpc • Mvir =6.3E14 M⊙ • K-band surface brightness: • μk =20 m/acrsec2 • ~100 M⊙/pc2 • Definition of “galaxies” • Population of Satellites • Alignment of Satellites • Clustering of “galaxies” • “Color” of “galaxies” • Intra-cluster “Stars” • Angular momentum • Dynamic of Sinking Satellites

  22. Probability of Mis-alignment angleoverall alignment: total mass vs “BCG” Results implied by weak lensing: about 30 degree, Okumura & Jing, 2009; Okumura, Jing & Li, 2009

  23. The half stellar mass radii of haloes

  24. The axis ratio at half stellar mass radii

  25. summary • Non-radiative gas alter matter distribution slightly, including gas-cooling, star formation process will make the matter distribution more concentrated (+10 to20% )and cuspy; • The halos with gas cooling and star formation become significantly more spherical than those in N-body simulation; • The projected mass distribution: at radii about 15 kpc/h or 5% Virial Radii, the major axis of stellar components are well-aligned with that of total mass with mis-alignment angle less than 10 degree, consistent with obs. • The mis-alignment angle between “BCG” orientation and host halo major axis is about 30 degree, consistent with results implied by weak lensing observations Caution: numerical effects, over-cooling and over-stripping

  26. Open issues • Definition of “galaxies” • Population of Satellites • Alignment of Satellites • Clustering of “galaxies” • “Color” of “galaxies” • Intra-cluster “Stars” • Angular momentum • Dynamic of Sinking Satellites • Numerical effects • Over-Cooling • Over-Merging/Stripping

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